const fp = require('lodash/fp');
// 数据
// horsepower 马力, dollar_value 价格，in_stock 库存
const cars = [
    {name: 'Ferrari FF', horsepower: 660, dollar_value: 700000, in_stock: true},
    {name: 'Spyker C12 Zagato', horsepower: 650, dollar_value: 648000, in_stock: false},
    {name: 'Jaguar XKR-S', horsepower: 550, dollar_value: 13200, in_stock: false},
    {name: 'Audi R8', horsepower: 525, dollar_value: 114200, in_stock: false},
    {name: 'Aston Martin One-77', horsepower: 750, dollar_value: 1850000, in_stock: true},
    {name: 'Pagani Huayra', horsepower: 700, dollar_value: 1300000, in_stock: false},
];


// 练习1 ：flowRight 从右至左执行
const isLastInStock = fp.flowRight(fp.prop('in_stock'), fp.last);
console.log(isLastInStock(cars));

// 练习2 ：调用fp.first 即可
const isFristName = fp.flowRight(fp.prop('name'), fp.first);
console.log(isFristName(cars));

// 练习3 :
let _average = function (xs) {
    return fp.reduce(fp.add, 0, xs) / xs.length;
}

// 用函数封装一下，返回 car 的 dollar_value 数组
let dollar_values = function (cars) {
    return fp.map(function(car) {
        return car.dollar_value;
    }, cars);
}
// 解法一： 实现一个简单的组合函数
function compose (f, g) {
    return function (value) {
        return f(g(value));
    }
}
const averageDollarValue1 = compose(_average, dollar_values);
console.log(averageDollarValue1(cars));

// 解法二： 可以直接调用 fp.flowRight 来实现
const averageDollarValue2 = fp.flowRight(_average, dollar_values);
console.log(averageDollarValue2(cars));

// 练习4
let _underscore = fp.replace(/\W+/g, '_');
const sanitizeNames = fp.flowRight( _underscore, fp.map(fp.lowerCase), fp.split(' '));
console.log(sanitizeNames(["Hello World"]));